Uranus

Mercury (planet) Mercury is gravitationally locked and rotates in a way that is unique in the Solar System. As seen relative to the fixed stars, it rotates exactly three times for every two revolutions[b] it makes around its orbit.[13] As seen from the Sun, in a frame of reference that rotates with the orbital motion, it appears to rotate only once every two Mercurian years. An observer on Mercury would therefore see only one day every two years. Because Mercury's orbit lies within Earth's orbit (as does Venus's), it can appear in Earth's sky in the morning or the evening, but not in the middle of the night. Also, like Venus and the Moon, it displays a complete range of phases as it moves around its orbit relative to Earth. Although Mercury can appear as a very bright object when viewed from Earth, its proximity to the Sun makes it more difficult to see than Venus. Internal structure Internal structure of Mercury: 1. Mercury's density can be used to infer details of its inner structure. Surface geology

Saturn Saturn's interior is probably composed of a core of iron, nickel and rock (silicon and oxygen compounds), surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium and an outer gaseous layer.[15] The planet exhibits a pale yellow hue due to ammonia crystals in its upper atmosphere. Electrical current within the metallic hydrogen layer is thought to give rise to Saturn's planetary magnetic field, which is weaker than Earth's magnetic field but has a magnetic moment 580 times that of the Earth due to Saturn's larger body radius. Saturn's magnetic field strength is around one-twentieth the strength of Jupiter's.[16] The outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h (1,100 mph), faster than on Jupiter, but not as fast as those on Neptune.[17] Physical characteristics Composite image roughly comparing the sizes of Saturn and Earth Atmosphere

Earth Earth is the third planet from the Sun. It is the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. Earth formed approximately 4.54 billion years ago, and life appeared on its surface within its first billion years.[24] Earth's biosphere then significantly altered the atmospheric and other basic physical conditions, which enabled the proliferation of organisms as well as the formation of the ozone layer, which together with Earth's magnetic field blocked harmful solar radiation, and permitted formerly ocean-confined life to move safely to land.[25] The physical properties of the Earth, as well as its geological history and orbit, have allowed life to persist. Name and etymology The modern English noun earth developed from Middle English erthe (recorded in 1137), itself from Old English eorthe (dating from before 725), deriving from Proto-Germanic *erthō. Composition and structure Shape Heat Surface

Mars Animation of Mars' rotation from the vantage of an observer who moves south, then north, to hover over both poles, showing the planet's major topographic features. Mars is currently host to five functioning spacecraft: three in orbit – the Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter – and two on the surface – Mars Exploration Rover Opportunity and the Mars Science Laboratory Curiosity. Defunct spacecraft on the surface include MER-A Spirit and several other inert landers and rovers such as the Phoenix lander, which completed its mission in 2008. Observations by the Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.[25] In 2013, NASA's Curiosity rover discovered that Mars' soil contains between 1.5% and 3% water by mass (about two pints of water per cubic foot or 33 liters per cubic meter, albeit attached to other compounds and thus not freely accessible).[26] Physical characteristics Size comparison of Earth and Mars. Soil

Venus Venus is a terrestrial planet and is sometimes called Earth's "sister planet" because of their similar size, gravity, and bulk composition (Venus is both the closest planet to Earth and the planet closest in size to Earth). However, it has also been shown to be very different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. Physical characteristics Venus is one of the four terrestrial planets in the Solar System, meaning that, like Earth, it is a rocky body. Geography The Venusian surface was a subject of speculation until some of its secrets were revealed by planetary science in the 20th century. About 80% of the Venusian surface is covered by smooth, volcanic plains, consisting of 70% plains with wrinkle ridges and 10% smooth or lobate plains.[21] Two highland "continents" make up the rest of its surface area, one lying in the planet's northern hemisphere and the other just south of the equator.

Neptune Neptune is similar in composition to Uranus, and both have compositions which differ from those of the larger gas giants, Jupiter, and Saturn. Neptune's atmosphere, while similar to Jupiter's and Saturn's in that it is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, contains a higher proportion of "ices" such as water, ammonia, and methane. Astronomers sometimes categorise Uranus and Neptune as "ice giants" in order to emphasise these distinctions.[10] The interior of Neptune, like that of Uranus, is primarily composed of ices and rock.[11] It is possible that the core has a solid surface, but the temperature would be thousands of degrees and the atmospheric pressure crushing.[12] Traces of methane in the outermost regions in part account for the planet's blue appearance.[13] In contrast to the hazy, relatively featureless atmosphere of Uranus, Neptune's atmosphere is notable for its active and visible weather patterns. History Naming

Jupiter Structure Jupiter is composed primarily of gaseous and liquid matter. It is the largest of four gas giants as well as the largest planet in the Solar System with a diameter of 142,984 km (88,846 mi) at its equator. The density of Jupiter, 1.326 g/cm3, is the second highest of the gas giants, but lower than for any of the four terrestrial planets. Composition Jupiter's upper atmosphere is composed of about 88–92% hydrogen and 8–12% helium by percent volume or fraction of gas molecules. Based on spectroscopy, Saturn is thought to be similar in composition to Jupiter, but the other gas giants Uranus and Neptune have relatively much less hydrogen and helium.[21] Because of the lack of atmospheric entry probes, high-quality abundance numbers of the heavier elements are lacking for the outer planets beyond Jupiter. Mass Jupiter's diameter is one order of magnitude smaller (×0.10045) than the Sun, and one order of magnitude larger (×10.9733) than the Earth. Internal structure Atmosphere Cloud layers